I would cut a slit or drill 3 holes
But an idea to consider with the holes is to make it not all thew way to the bottom.. too allow some to top drain... that way you store mycorrhizal inside hollow tree along with all sorts of nutrients:
"Fast forward 11 years to 2018, when I flew to Basque France to attend a conference on pollarding. It was there, surrounded by European foresters, forest engineers and horticulturalists, that everyone had a special place in their soul for heart rot and hollow trees, something I had never encountered before. A prevailing opinion, which I now view as a bridge between forest ecology and horticulture, was that heart rot creates hollows/habitats for all sorts of fauna. In hosting this fauna, the trees become collectors of poo (feces, not the bear). This creates an incredible microbial metabolism in the tree which, when combined with decomposing heartwood full of trapped minerals, supplies a steady amount of organic fertilizer that is slowly released to the base of the tree. Since trees store growth rings in the heartwood on an annual basis, this natural process of decomposition and fertilizing is a renewable. Hollow trees provide their own
compost. That’s true sustainability." -Eliza Hog tree farm